ALBUQUERQUE, NM - The ABQ BioPark's Aquatic Conservation Facility expects to release nearly 90,000 endangered Rio Grande silvery minnows this year - an increase in production of more than 70 percent from last year.

"We had really good results with both captive spawning and survival of larval fish this year," said Kathy Lang, curator of the Aquatic Conservation Facility.

Staff released 42,000 fish last week and will release more than 47,000 on November 19 and 20.

Lang said the facility made some changes to enhance larval survival this year, including growing its own algae and rotifers for fish food.

At the same time, the wild population fared well, so fewer overall fish were required to supplement the wild population.

"This was actually a fair year for water conditions in the river, which is good for the species, so fewer captive-spawned fish were required to supplement the wild fish," Lang said. "And we are optimistic about river conditions next year."

The Aquatic Conservation Facility is one of three in New Mexico that are cooperating to raise the endangered fish. Because of the facility's success this year, it provided a larger percentage than usual for the annual minnow release.

The silvery minnow, a 2- to 4-inch long fish, was once one of the most common species in the Rio Grande, but by 1994 its population had declined so greatly that it was added to the federal Endangered Species List.

Since it opened in 2003, the Aquatic Conservation Facility has released about 670,000 minnows (including this year's release). The growing operation is staffed by three full-time employees and three seasonal workers and receives supplemental funding from grants.

The BioPark has been part of the species recovery program since 2000. Each spring, staff collect eggs from the Rio Grande to hatch in tanks at the BioPark and also breed additional minnows from previously collected broodstock. Minnows are tagged each fall before their release so the Fish and Wildlife Service (FWS) can monitor how successful the program is. Tagging also allows FWS to monitor some aspects of the minnow's behavior and how long the fish are surviving in different parts of the river.